Overview

Unless otherwise noted, the term switch refers to a standalone switch and to a switch stack.

In this document, IP refers to IP Version 4 (IPv4) unless there is a specific reference to IP Version 6 (IPv6).

Features

The switch ships with either of these software images installed:

•IP base image (formerly known as the standard multilayer image [SMI]), which provides Layer 2+ features (enterprise-class intelligent services). These features include access control lists (ACLs), quality of service (QoS), static routing, the Hot Standby Router Protocol (HSRP), and the Routing Information Protocol (RIP). Switches with the IP base image installed can be upgraded to IP services image (formerly known as the enhanced multilayer image [EMI].)

•IP services image, which provides a richer set of enterprise-class intelligent services. It includes all IP base image features plus full Layer 3 routing (IP unicast routing, IP multicast routing, and fallback bridging). To distinguish it from the Layer 2+ static routing and RIP, the IP services image includes protocols such as the Enhanced Interior Gateway Routing Protocol (EIGRP) and the Open Shortest Path First (OSPF) Protocol.

Note Unless otherwise noted all features described in this chapter and in this guide are supported on both the IP base image and the IP services image.

For IPv6 capability, the switch must be running the advanced IP services image. You can order this image upgrade from Cisco. The advanced IP services image includes all IP services image features plus IPv6 host and unicast routing support.

Some features in this chapter are available only on the cryptographic (supports encryption) versions of the software IP base and IP services images. You must obtain authorization to use this feature and to download the cryptographic version of the software from Cisco.com. For more information, see the release notes for this release.

Ease-of-Use and Ease-of-Deployment Features

•Express Setup for quickly configuring a switch for the first time with basic IP information, contact information, switch and Telnet passwords, and Simple Network Management Protocol (SNMP) information through a browser-based program. For more information about Express Setup, see the getting started guide.

•User-defined and Cisco-default Smartports macros for creating custom switch configurations for simplified deployment across the network.

•An embedded device manager GUI for configuring and monitoring a single switch through a web browser. For information about launching the device manager, see the getting started guide. For more information about the device manager, see the switch online help.

•Cisco Network Assistant (hereafter referred to as Network Assistant) for

–Managing communities, which are device groups like clusters, except that they can contain routers and access points and can be made more secure.

–Interactive guide mode that guides you in configuring complex features such as VLANs, ACLs, and quality of service (QoS).

–Configuration wizards that prompt you to provide only the minimum required information to configure complex features such as QoS priorities for video traffic, priority levels for data applications, and security.

–Downloading an image to a switch.

–Applying actions to multiple ports and multiple switches at the same time, such as VLAN and QoS settings, inventory and statistic reports, link- and switch-level monitoring and troubleshooting, and multiple switch software upgrades.

–Viewing a topology of interconnected devices to identify existing switch clusters and eligible switches that can join a cluster and to identify link information between switches.

–Monitoring real-time status of a switch or multiple switches from the LEDs on the front-panel images. The system, redundant power system (RPS), and port LED colors on the images are similar to those used on the physical LEDs.

•Cisco StackWise technology for

–Connecting up to nine switches through their StackWise ports and operating as a single switch or switch-router in the network.

–Creating a bidirectional 32-Gbps switching fabric across the switch stack, where all stack members have full access to the system bandwidth.

–Using a single IP address and configuration file to manage the entire switch stack.

–Automatic Cisco IOS version-check of new stack members with the option to automatically load images from the stack master or from a TFTP server.

–Adding, removing, and replacing switches in the stack without disrupting the operation of the stack.

–Provisioning a new member for a switch stack with the offline configuration feature. You can configure in advance the interface configuration for a specific stack member number and for a specific switch type of a new switch that is not part of the stack. The switch stack retains this information across stack reloads whether or not the provisioned switch is part of the stack.

–Displaying stack-ring activity statistics (the number of frames sent by each stack member to the ring).

•Multicast VLAN registration (MVR) to continuously send multicast streams in a multicast VLAN while isolating the streams from subscriber VLANs for bandwidth and security reasons

•IGMP filtering for controlling the set of multicast groups to which hosts on a switch port can belong

•IGMP throttling for configuring the action when the maximum number of entries is in the IGMP forwarding table

•IGMP leave timer to configure the leave latency for the network.

•Switch Database Management (SDM) templates for allocating system resources to maximize support for user-selected features

Management Options

•An embedded device manager—The device manager is a GUI that is integrated in the software image. You use it to configure and to monitor a single switch. For information about launching the device manager, see the getting started guide. For more information about the device manager, see the switch online help.

•Network Assistant—Network Assistant is a network management application that can be downloaded from Cisco.com. You use it to manage a single switch, a cluster of switches, or a community of devices. For more information about Network Assistant, see Getting Started with Cisco Network Assistant, available on Cisco.com.

•CLI—The Cisco IOS software supports desktop- and multilayer-switching features. You can access the CLI either by connecting your management station directly to the switch console port or by using Telnet from a remote management station. You can manage the switch stack by connecting to the console port of any stack member. For more information about the CLI, see "Using the Command-Line Interface."

•SNMP—SNMP management applications such as CiscoWorks2000 LAN Management Suite (LMS) and HP OpenView. You can manage from an SNMP-compatible management station that is running platforms such as HP OpenView or SunNet Manager. The switch supports a comprehensive set of MIB extensions and four remote monitoring (RMON) groups. For more information about using SNMP, see Chapter 31, "Configuring SNMP."

•IE2100—Cisco Intelligence Engine 2100 Series Configuration Registrar is a network management device that works with embedded Cisco Networking Services (CNS) Agents in the switch software. You can automate initial configurations and configuration updates by generating switch-specific configuration changes, sending them to the switch, executing the configuration change, and logging the results.

•In-band management access for up to 16 simultaneous Telnet connections for multiple CLI-based sessions over the network

•In-band management access for up to five simultaneous, encrypted Secure Shell (SSH) connections for multiple CLI-based sessions over the network (requires the cryptographic versions of the software IP base and IP services images)

•In-band management access through SNMP Versions 1, 2c, and 3 get and set requests

•Out-of-band management access through the switch console port to a directly attached terminal or to a remote terminal through a serial connection or a modem

–UplinkFast, cross-stack UplinkFast, and BackboneFast for fast convergence after a spanning-tree topology change and for achieving load balancing between redundant uplinks, including Gigabit uplinks and cross-stack Gigabit uplinks

•IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) for grouping VLANs into a spanning-tree instance and for providing multiple forwarding paths for data traffic and load balancing and rapid per-VLAN Spanning-Tree plus (rapid-PVST+) based on the IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) for rapid convergence of the spanning tree by immediately transitioning root and designated ports to the forwarding state

•Optional spanning-tree features available in PVST+, rapid-PVST+, and MSTP mode:

–Port Fast for eliminating the forwarding delay by enabling a port to immediately transition from the blocking state to the forwarding state

–Loop guard for preventing alternate or root ports from becoming designated ports because of a failure that leads to a unidirectional link

•Equal-cost routing for link-level and switch-level redundancy

•Flex Link Layer 2 interfaces to back up one another as an alternative to STP for basic link redundancy

•RPS support through the Cisco RPS 300 and Cisco RPS 675 for enhancing power reliability

VLAN Features

•Support for up to 1005 VLANs for assigning users to VLANs associated with appropriate network resources, traffic patterns, and bandwidth

•Support for VLAN IDs in the full 1 to 4094 range allowed by the IEEE 802.1Q standard

•VLAN Query Protocol (VQP) for dynamic VLAN membership

•Inter-Switch Link (ISL) and IEEE 802.1Q trunking encapsulation on all ports for network moves, adds, and changes; management and control of broadcast and multicast traffic; and network security by establishing VLAN groups for high-security users and network resources

•Dynamic Trunking Protocol (DTP) for negotiating trunking on a link between two devices and for negotiating the type of trunking encapsulation (IEEE 802.1Q or ISL) to be used

•VLAN1 minimization for reducing the risk of spanning-tree loops or storms by allowing VLAN 1 to be disabled on any individual VLAN trunk link. With this feature enabled, no user traffic is sent or received on the trunk. The switch CPU continues to send and receive control protocol frames.

•Private VLANs to address VLAN scalability problems, to provide a more controlled IP address allocation, and to allow Layer 2 ports to be isolated from other ports on the switch

•IP source guard to restrict traffic on nonrouted interfaces by filtering traffic based on the DHCP snooping database and IP source bindings

•Dynamic ARP inspection to prevent malicious attacks on the switch by not relaying invalid ARP requests and responses to other ports in the same VLAN

•IEEE 802.1Q tunneling so that customers with users at remote sites across a service-provider network can keep VLANs segregated from other customers and Layer 2 protocol tunneling to ensure that the customer's network has complete STP, CDP, and VTP information about all users

–IP ToS/DSCP and IEEE 802.1p CoS marking based on flow-based packet classification (classification based on information in the MAC, IP, and TCP/UDP headers) for high-performance quality of service at the network edge, allowing for differentiated service levels for different types of network traffic and for prioritizing mission-critical traffic in the network

–Trusted port states (CoS, DSCP, and IP precedence) within a QoS domain and with a port bordering another QoS domain

–Trusted boundary for detecting the presence of a Cisco IP phone, trusting the CoS value received, and ensuring port security

•Policing

–Traffic-policing policies on the switch port for managing how much of the port bandwidth should be allocated to a specific traffic flow

–Weighted tail drop (WTD) as the congestion-avoidance mechanism for managing the queue lengths and providing drop precedences for different traffic classifications

–Shaped round robin (SRR) as the scheduling service for specifying the rate at which packets are dequeued to the stack ring (sharing is the only supported mode on ingress queues)

•Egress queues and scheduling

–Four egress queues per port

–WTD as the congestion-avoidance mechanism for managing the queue lengths and providing drop precedences for different traffic classifications

–SRR as the scheduling service for specifying the rate at which packets are dequeued to the egress interface (shaping or sharing is supported on egress queues). Shaped egress queues are guaranteed but limited to using a share of port bandwidth. Shared egress queues are also guaranteed a configured share of bandwidth, but can use more than the guarantee if other queues become empty and do not use their share of the bandwidth.

Layer 3 Features

Note Some features noted in this section are available only on the IP services image.

•Fallback bridging for forwarding non-IP traffic between two or more VLANs (requires the IP services image)

•Static IP routing for manually building a routing table of network path information

•Equal-cost routing for load balancing and redundancy

•Internet Control Message Protocol (ICMP) and ICMP Router Discovery Protocol (IRDP) for using router advertisement and router solicitation messages to discover the addresses of routers on directly attached subnets

•Protocol-Independent Multicast (PIM) for multicast routing within the network, allowing for devices in the network to receive the multicast feed requested and for switches not participating in the multicast to be pruned. Includes support for PIM sparse mode (PIM-SM), PIM dense mode (PIM-DM), and PIM sparse-dense mode (requires the IP services image)

•Nonstop forwarding (NSF) awareness to enable the Layer 3 switch to continue forwarding packets from an NSF-capable neighboring router when the primary route processor (RP) is failing and the backup RP is taking over, or when the primary RP is manually reloaded for a nondisruptive software upgrade (requires the IP services image)

Power over Ethernet Features

•Ability to provide power to connected Cisco pre-standard and IEEE 802.3af-compliant powered devices from Power over Ethernet (PoE)-capable ports if the switch detects that there is no power on the circuit.

•Support for CDP with power consumption. The powered device notifies the switch of the amount of power it is consuming.

•Support for Cisco intelligent power management. The powered device and the switch negotiate through power-negotiation CDP messages for an agreed power-consumption level. The negotiation allows a high-power Cisco powered device to operate at its highest power mode.

•Automatic detection and power budgeting; the switch maintains a power budget, monitors and tracks requests for power, and grants power only when it is available.

Monitoring Features

•Switch LEDs that provide port-, switch-, and stack-level status

•MAC address notification traps and RADIUS accounting for tracking users on a network by storing the MAC addresses that the switch has learned or removed

•Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) for traffic monitoring on any port or VLAN

Default Settings After Initial Switch Configuration

The switch is designed for plug-and-play operation, requiring only that you assign basic IP information to the switch and connect it to the other devices in your network. If you have specific network needs, you can change the interface-specific and system- and stack-wide settings.

Note For information about assigning an IP address by using the browser-based Express Setup program, see the getting started guide. For information about assigning an IP address by using the CLI-based setup program, see the hardware installation guide.

If you do not configure the switch at all, the switch operates with these default settings:

Network Configuration Examples

This section provides network configuration concepts and includes examples of using the switch to create dedicated network segments and interconnecting the segments through Fast Ethernet and Gigabit Ethernet connections.

Design Concepts for Using the Switch

As your network users compete for network bandwidth, it takes longer to send and receive data. When you configure your network, consider the bandwidth required by your network users and the relative priority of the network applications they use.

Table 1-1 describes what can cause network performance to degrade and how you can configure your network to increase the bandwidth available to your network users.

Table 1-1 Increasing Network Performance

Network Demands

Suggested Design Methods

Too many users on a single network segment and a growing number of users accessing the Internet

•Create smaller network segments so that fewer users share the bandwidth, and use VLANs and IP subnets to place the network resources in the same logical network as the users who access those resources most.

•Use full-duplex operation between the switch and its connected workstations.

•Increased power of new PCs, workstations, and servers

•High bandwidth demand from networked applications (such as e-mail with large attached files) and from bandwidth-intensive applications (such as multimedia)

•Connect global resources—such as servers and routers to which the network users require equal access—directly to the high-speed switch ports so that they have their own high-speed segment.

•Use the EtherChannel feature between the switch and its connected servers and routers.

Bandwidth alone is not the only consideration when designing your network. As your network traffic profiles evolve, consider providing network services that can support applications for voice and data integration, multimedia integration, application prioritization, and security. Table 1-2 describes some network demands and how you can meet them.

•Use other QoS mechanisms such as packet classification, marking, scheduling, and congestion avoidance to classify traffic with the appropriate priority level, thereby providing maximum flexibility and support for mission-critical, unicast, and multicast and multimedia applications.

•Use MVR to continuously send multicast streams in a multicast VLAN but to isolate the streams from subscriber VLANs for bandwidth and security reasons.

High demand on network redundancy and availability to provide always on mission-critical applications

•Use switch stacks, where all stack members are eligible stack masters in case of stack-master failure. All stack members have synchronized copies of the saved and running configuration files of the switch stack.

A growing demand for using existing infrastructure to transport data and voice from a home or office to the Internet or an intranet at higher speeds

Use the Catalyst Long-Reach Ethernet (LRE) switches to provide up to 15 Mb of IP connectivity over existing infrastructure, such as existing telephone lines.

Note LRE is the technology used in the Catalyst 2900 LRE XL and Catalyst 2950 LRE switches. See the documentation sets specific to these switches for LRE information.

•You can use the switches and switch stacks to create the following:

•Cost-effective wiring closet (Figure 1-1)—A cost-effective way to connect many users to the wiring closet is to have a switch stack of up to nine Catalyst 3750 switches. To preserve switch connectivity if one switch in the stack fails, connect the switches as recommended in the hardware installation guide, and enable either cross-stack Etherchannel or cross-stack UplinkFast.

You can have redundant uplink connections, using SFP modules in the switch stack to a Gigabit backbone switch, such as a Catalyst 4500 or Catalyst 3750-12S Gigabit switch. You can also create backup paths by using Fast Ethernet, Gigabit, or EtherChannel links. If one of the redundant connections fails, the other can serve as a backup path. If the Gigabit switch is cluster-capable, you can configure it and the switch stack as a switch cluster to manage them through a single IP address. The Gigabit switch can be connected to a Gigabit server through a 1000BASE-T connection.

Figure 1-1 Cost-Effective Wiring Closet

•High-performance wiring closet (Figure 1-2)—For high-speed access to network resources, you can use Catalyst 3750switches and switch stacks in the access layer to provide Gigabit Ethernet to the desktop. To prevent congestion, use QoS DSCP marking priorities on these switches. For high-speed IP forwarding at the distribution layer, connect the switches in the access layer to a Gigabit multilayer switch in the backbone, such as a Catalyst 4500 Gigabit switch or Catalyst 6500 Gigabit switch.

Each switch in this configuration provides users with a dedicated 1-Gbps connection to network resources. Using SFP modules also provides flexibility in media and distance options through fiber-optic connections.

Figure 1-2 High-Performance Wiring Closet

•Redundant Gigabit backbone—Using HSRP, you can create backup paths between two Catalyst 3750G multilayer Gigabit switches to enhance network reliability and load balancing for different VLANs and subnets. Using HSRP also provides faster network convergence if any network failure occurs. You can connect the Catalyst switches, again in a star configuration, to two Catalyst 3750G multilayer backbone switches. If one of the backbone switches fails, the second backbone switch preserves connectivity between the switches and network resources.

Figure 1-3 Redundant Gigabit Backbone

•Server aggregation (Figure 1-4) and Linux server cluster (Figure 1-5)—You can use the switches and switch stacks to interconnect groups of servers, centralizing physical security and administration of your network. For high-speed IP forwarding at the distribution layer, connect the switches in the access layer to multilayer switches with routing capability. The Gigabit interconnections minimize latency in the data flow.

QoS and policing on the switches provide preferential treatment for certain data streams, if required. They segment traffic streams into different paths for processing. Security features on the switch ensure rapid handling of packets.

Dual homing of servers to dual switch stacks with redundant Gigabit EtherChannel and cross-stack EtherChannel provide fault tolerance from the server racks to the core.

Using dual SFP module uplinks from the switches provides redundant uplinks to the network core. Using SFP modules provides flexibility in media and distance options through fiber-optic connections.

The various lengths of stack cable available, ranging from 0.5 meter to 3 meters provide extended connections to the switch stacks across multiple server racks, for multiple stack aggregation.

Figure 1-4 Server Aggregation

Figure 1-5 Linux Server Cluster

Small to Medium-Sized Network Using Catalyst 3750 Switches

Figure 1-6 shows a configuration for a network of up to 500 employees. This network uses a Catalyst 3750 Layer 3 switch stack with high-speed connections to two routers. For network reliability and load balancing, this network has HSRP enabled on the routers and on the switches. This ensures connectivity to the Internet, WAN, and mission-critical network resources in case one of the routers or switches fails. The switches are using routed uplinks for faster failover. They are also configured with equal-cost routing for load sharing and redundancy. (A Layer 2 switch stack can use cross-stack EtherChannel for load sharing.)

The switches are connected to workstations, local servers, and IEEE 802.3af compliant and noncompliant powered devices (such as Cisco IP Phones). The server farm includes a call-processing server running Cisco CallManager software. Cisco CallManager controls call processing, routing, and IP phone features and configuration. The switches are interconnected through Gigabit interfaces.

This network uses VLANs to logically segment the network into well-defined broadcast groups and for security management. Data and multimedia traffic are configured on the same VLAN. Voice traffic from the Cisco IP Phones are configured on separate VVIDs. If data, multimedia, and voice traffic are assigned to the same VLAN, only one VLAN can be configured per wiring closet.

When an end station in one VLAN needs to communicate with an end station in another VLAN, a router or Layer 3 switch routes the traffic to the appropriate destination VLAN. In this network, the switch stack is providing inter-VLAN routing. VLAN access control lists (VLAN maps) on the switch stack provide intra-VLAN security and prevent unauthorized users from accessing critical pieces of the network.

In addition to inter-VLAN routing, the multilayer switches provide QoS mechanisms such as DSCP priorities to prioritize the different types of network traffic and to deliver high-priority traffic in a predictable manner. If congestion occurs, QoS drops low-priority traffic to allow delivery of high-priority traffic.

Catalyst PoE switch ports automatically detect any Cisco pre-standard and IEEE 802.3af-compliant powered devices that are connected. Each PoE switch port provides 15.4 W of power per port. The powered device, such as an IP phone, can receive redundant power when it is also connected to an AC power source. Powered devices not connected to Catalyst PoE switches must be connected to AC power sources to receive power.

Cisco CallManager controls call processing, routing, and IP phone features and configuration. Users with workstations running Cisco SoftPhone software can place, receive, and control calls from their PCs. Using Cisco IP Phones, Cisco CallManager software, and Cisco SoftPhone software integrates telephony and IP networks, and the IP network supports both voice and data.

Large Network Using Catalyst 3750 Switches

Switches in the wiring closet have traditionally been only Layer 2 devices, but as network traffic profiles evolve, switches in the wiring closet are increasingly employing multilayer services such as multicast management and traffic classification. Figure 1-7 shows a configuration for a network that only use Catalyst 3750 multilayer switch stacks in the wiring closets and two backbone switches, such as the Catalyst 6500 switches, to aggregate up to ten wiring closets.

In the wiring closet, each switch stack has IGMP snooping enabled to efficiently forward multimedia and multicast traffic. QoS ACLs that either drop or mark nonconforming traffic based on bandwidth limits are also configured on each switch stack. VLAN maps provide intra-VLAN security and prevent unauthorized users from accessing critical pieces of the network. QoS features can limit bandwidth on a per-port or per-user basis. The switch ports are configured as either trusted or untrusted. You can configure a trusted port to trust the CoS value, the DSCP value, or the IP precedence. If you configure the port as untrusted, you can use an ACL to mark the frame in accordance with the network policy.

Each switch stack provides inter-VLAN routing. They provide proxy ARP services to get IP and MAC address mapping, thereby removing this task from the routers and decreasing this type of traffic on the WAN links. These switch stacks also have redundant uplink connections to the backbone switches, with each uplink port configured as a trusted routed uplink to provide faster convergence in case of an uplink failure.

The routers and backbone switches have HSRP enabled for load balancing and redundant connectivity to guarantee mission-critical traffic.

Multidwelling Network Using Catalyst 3750 Switches

A growing segment of residential and commercial customers are requiring high-speed access to Ethernet metropolitan-area networks (MANs). Figure 1-8 shows a configuration for a Gigabit Ethernet MAN ring using multilayer switch stacks as aggregation switches in the mini-point-of-presence (POP) location. These switches are connected through 1000BASE-X SFP module ports.

The resident switches can be Catalyst 3750 switches, providing customers with high-speed connections to the MAN. Catalyst 2900 LRE XL and Catalyst 2950 LRE switches also can be used as residential switches for customers requiring connectivity through existing phone lines. The Catalyst 2900 LRE XL and Catalyst 2950 LRE switches can then connect to another residential switch or to a Catalyst 3750 aggregation switch. For more information about the Catalyst Long-Reach Ethernet (LRE) switches, see the documentation sets specific to these switches for LRE information.

All ports on the residential Catalyst 3750 switches (and Catalyst 2950 LRE switches if they are included) are configured as IEEE 802.1Q trunks with protected port and STP root guard features enabled. The protected port feature provides security and isolation between ports on the switch, ensuring that subscribers cannot view packets destined for other subscribers. STP root guard prevents unauthorized devices from becoming the STP root switch. All ports have IGMP snooping or CGMP enabled for multicast traffic management. ACLs on the uplink ports to the aggregating Catalyst 3750 multilayer switches provide security and bandwidth management.

Long-Distance, High-Bandwidth Transport Configuration

Figure 1-9 shows a configuration for sending 8 Gigabits of data over a single fiber-optic cable. The Catalyst 3750 switches have Coarse Wave Division Multiplexer (CWDM) fiber-optic SFP modules installed. Depending on the CWDM SFP module, data is sent at wavelengths from 1470 to 1610 nm. The higher the wavelength, the farther the transmission can travel. A common wavelength used for long-distance transmissions is 1550 nm.

The CWDM SFP modules connect to CWDM optical add/drop multiplexer (OADM) modules over distances of up to 393,701 feet (74.5 miles or 120 km). The CWDM OADM modules combine (or multiplex) the different CWDM wavelengths, allowing them to travel simultaneously on the same fiber-optic cable. The CWDM OADM modules on the receiving end separate (or demultiplex) the different wavelengths.

For more information about the CWDM SFP modules and CWDM OADM modules, see the Cisco CWDM GBIC and CWDM SFP Installation Note.

Figure 1-9 Long-Distance, High-Bandwidth Transport Configuration

Where to Go Next

Before configuring the switch, review these sections for startup information: